/*
   种树
 */

public class WorkTest120201 {
    public static void main(String[] args){
        int tree = 1;
        int sum = 0;
        for(int i =1;i<=20;i++){
            sum += tree;
            tree++;
        }
        int sum1 = sum *60;
        System.out.println(sum1+"棵");
    }

}
